The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Referring now to FIG. 1, a functional block diagram of an engine system 100 is presented. Air is drawn into an engine 102 through an intake manifold 104. A throttle valve 106 varies the volume of air drawn into the intake manifold 104. The air mixes with fuel from one or more fuel injectors 108 to form an air and fuel (A/F) mixture. The A/F mixture is combusted within one or more cylinders of the engine 102, such as cylinder 110. In various engine systems, such as the engine system 100, combustion may be initiated by spark from a spark plug 112. Resulting exhaust is expelled from the cylinders to an exhaust system 114.
The exhaust system 114 includes an oxygen sensor 116 that measures and outputs the concentration of oxygen in the exhaust. The oxygen sensor 116 includes a heater that receives power from a heater power supply 118. The heater may be used to bias the oxygen sensor 116 to within an operating temperature range.
An engine control module (ECM) 120 receives the output of the oxygen sensor 116 and may receive signals from other sensors 122. The other sensors 122 may include, for example, a manifold absolute pressure (MAP) sensor and intake air temperature (IAT) sensor. The ECM 120 controls the A/F mixture based on the output of the oxygen sensor 116. Additionally, the ECM 120 may control the A/F mixture based on the signals from the other sensors 122.
The temperature of the oxygen sensor 116 is likely low when the engine 102 is started. Accordingly, the output of the oxygen sensor 116 is likely unreliable after engine startup. When the output of the oxygen sensor 116 is unreliable, the ECM 120 may control the A/F mixture independent of the output of the oxygen sensor 116.
The ECM 120 may estimate that the output of the oxygen sensor 116 will be reliable when a timer expires after the output leaves a calibratable voltage window. For example, the ECM 120 may estimate that the output of the oxygen sensor 116 will be reliable twenty (20) seconds after the output leaves the voltage window. In such implementations, the ECM 120 may estimate that the output of the oxygen sensor 116 will be reliable approximately thirty-five (35) seconds after engine startup.